Of the bacterial constituents of dental plaque, the most well characterized organism with respect to oral disease is Streptococcus mutans. Another member of the oral Streptococci is Streptococcus sanguis, whose role in dental disease is poorly, if at all, understood. Some strains of this organism produce and secrete an IgAl protease, very similar to those enzymes that have been shown to be virulence factors in the gram-negative organisms Neisseria gonorrhoeae and Haemophilus influenzae. It is the goal of this project to gain an initial insight into the role of this enzyme, if any, in the etiology of oral disease. Using immunological, biochemical, and recombinant DNA techniques to clone the gene coding this enzyme, we will be able to lay the necessary foundation for future work to elucidate the mode of regulation of this enzyme and its role in dental disease. Information from this work will lead to a fuller understanding of the biology of Streptococcus sanguis, and will aid in the program to prevent and eventually eliminate dental disease.